Starch-based packaging material, apparatus and method for making same

Abstract

Starch-based packaging material and methods for making the material are described. The starch-based packaging material can comprise layers of expanded starch with a cellulosic web disposed between the layers. The expanded starch can be formed by extruding starch with water which acts as an expanding agent and causes the starch to expand resulting in an extrudate having a density of no more than about 5 lbs/ft 3 . An apparatus and methods for post-processing the expanded starch are described wherein the expanded starch is extruded as a tube that enters a funnel and is advanced forward by forced air. The tube passes over a blade where the tube is slit and subsequently opened up into a sheet by a second supply of forced air. The sheet then exits the funnel and can be calendered as well as stacked with subsequent lamination.

1 . A packaging material comprising
 a cellulosic web laminated between layers of expanded starch, free of added adhesive and with starch presenting surfaces on the outside of the layers.   
     
     
         2 . The packaging material of  claim 1  wherein the cellulosic web comprises paper towel material. 
     
     
         3 . The packaging material of  claim 1  wherein the expanded starch has a density of no more than about 5 lbs/ft 3 . 
     
     
         4 . The packaging material of  claim 1  wherein each of the layers of expanded starch comprises at least about 50 wt % starch. 
     
     
         5 . The packaging material of  claim 1  wherein the layers of expanded starch are fluted. 
     
     
         6 . The packaging material of  claim 1  wherein the packaging material comprises a stack of a plurality of alternating cellulosic webs between layers of expanded starch. 
     
     
         7 - 25 . (canceled) 
     
     
         26 . The packaging material of  claim 1  wherein the cellulosic web has a thickness no more than about 2 mm. 
     
     
         27 . The packaging material of  claim 1  wherein the cellulosic web comprises from about 60 wt % to about 100 wt % of cellulose fibers. 
     
     
         28 . The packaging material of  claim 1  wherein each of the layers of expanded starch comprises at least about 50 wt % starch and from about 2 wt % to about 30 wt % polyvinyl alcohol or copolymers thereof. 
     
     
         29 . The packaging material of  claim 1  wherein each of the layers of expanded starch further comprises up to about 10 wt % of an elastomeric or lower melting thermoplastic polymer. 
     
     
         30 . The packaging material of  claim 1  wherein the layers of expanded starch include fluted and nonfluted layers. 
     
     
         31 . The packaging material of  claim 1  wherein the packaging material is biodegradable.